Organocatalytic synthesis of new telechelic polycarbonates and study of their chemical reactivity

Article abstract of DOI:10.1016/j.polymer.2015.04.046

Abstract A two-step versatile process for telechelic polycarbonates synthesis is described. 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO₂) was used as thermolabile precursor of N-heterocyclic carbene (NHC) organocatalyst. In a first step, synthesized branched fatty diols or commercially available linear diols were reacted with an excess of dimethylcarbonate (DMC) to afford oligocarbonates with methylcarbonate end-groups. Then, the methylcarbonate groups were reacted with hydroxyl groups of 9-decen-1-ol, 4-hexyn-1-ol and 4-hydroxybenzene ethanol leading to telechelic oligomers with alkene, alkyne and phenol functionalities. Reactivity of these end-groups towards polymerization was successfully evidenced. This procedure could be used for preparing a range of new telechelic oligocarbonates.

Full text of DOI:10.1016/j.polymer.2015.04.046

Polymer 66 (2015) 127e134
Contents lists available at ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Organocatalytic synthesis of new telechelic polycarbonates and study
of their chemical reactivity
a
a,
Sandra Bigot , Nasreddine Kebir *, Laurent Plasseraud b, Fabrice Burel a
ꢀ
a
ꢀ
ꢀ
Normandie Universite, INSA de Rouen, CNRS UMR 6270 FR 3038, Avenue de l'universite BP08, 76801 Saint-Etienne du Rouvray, France
b
ꢀ
ꢀ
ꢀ
Institut de Chimie Moleculaire de l’Universite de Bourgogne (ICMUB), UMR CNRS 6302, UFR des Sciences et Techniques, 9 allee A. Savary, BP 47870, 21078
Dijon, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A
two-step versatile process for telechelic polycarbonates synthesis is described. 1-n-butyl-3-
Received 4 February 2015
Received in revised form
15 April 2015
Accepted 16 April 2015
Available online 23 April 2015
methylimidazolium-2-carboxylate (BMIM-2-CO2) was used as thermolabile precursor of N-heterocyclic
carbene (NHC) organocatalyst. In a first step, synthesized branched fatty diols or commercially available
linear diols were reacted with an excess of dimethylcarbonate (DMC) to afford oligocarbonates with
methylcarbonate end-groups. Then, the methylcarbonate groups were reacted with hydroxyl groups of
9-decen-1-ol, 4-hexyn-1-ol and 4-hydroxybenzene ethanol leading to telechelic oligomers with alkene,
alkyne and phenol functionalities. Reactivity of these end-groups towards polymerization was success-
fully evidenced. This procedure could be used for preparing a range of new telechelic oligocarbonates.
© 2015 Elsevier Ltd. All rights reserved.
Keywords:
Telechelic polycarbonate
Dimethylcarbonate
ADMET
1. Introduction
the catalytic active species [3e7]. 1,5,7-triazabicyclo[4,4,0]dec-5-
ene (TBD) was also used as an organocatalyst for the poly-
Polycarbonates (PCs) are a class of very important materials for
human life. They are used as engineering plastics thanks to many
properties such as transparency, toughness, biodegradability,
biocompatibility, thermal stability and mechanical durability.
Aliphatic PCs can be prepared through three pathways: (i) ring
opening polymerization of cyclic carbonates, (ii) copolymerization
of epoxides with carbon dioxide and (iii) polycondensation. In the
industry, PCs are still produced by polycondensation between
alkanediols and phosgene derivatives exhibiting toxological effetcs.
In this respect, the development of green and straightforward
processes for PCs elaboration is a subject of great interest and is still
under investigations [1]. Recently, aliphatic PCs have been syn-
thesized using dimethyl carbonate (DMC) as carbonyl source
instead of phosgene. DMC is an Eco-friendly product thanks to its
biodegradability and low toxicity (1000 times less than phosgene)
[2]. Naik et al. [3] have obtained polycarbonates by reacting DMC
from diols containing 3 to 6 carbons in presence of 1-n-butyl-3-
methylimidazolium-2-carboxylate (BMIM-2-CO2) as metal-free
pre-catalyst. Decarboxyaltion of BMIM-2-CO2 induced by heating
lead to the formation of an N-heterocyclic carbene (NHC) which is
condensation of diol and DMC [8]. Furthermore, polycarbonate
synthesis can be conducted by carbonate metathesis polymeriza-
tion using K2CO3 as catalyst [9].
Polymers are called “telechelic” when they contain two reactive
functional groups at their chain-ends. They are usually used for
synthesis of block copolymers and polymeric networks [10,11].
They also can be employed as linkers to modify properties of other
materials [12]. Few examples of telechelic polycarbonate synthesis
have been described in the literature. In 1994,
a,u-tertiary amino
and -quaternary ammonium polycarbonates have been syn-
a,u
thesized from bisphenol A and phosgene [13]. The functionalization
of the chain-ends was achieved with N,N0-dimethylaminophenol
and iodoammonium derivatives as chain limiters. Few years later,
Korn et al. [14] have prepared telechelic oligomers by depolymer-
ization of commercial bisphenol A polycarbonates in presence of
different diaryl carbonates (diphenylcarbonate, di-2-naphthyl car-
bonate, di-2-Allylphenyl carbonate and di-4-carbonitrile-4-
biphenyl carbonate) and tBuOK as catalyst.
Most of the prepared telechelic polycarbonates bear hydroxy
end-groups and are known as bis(hydroxy) polycarbonates (BHP).
They can be obtained by copolymerization of cyclohexene oxide
and carbon dioxide in presence of zinc catalyst [15], via poly-
condensation of bisphenol
A and diphenyl carbonate using
* Corresponding author.
ꢀ
lanthanum catalyst [16], or also by ring opening polymerization
E-mail address: nasreddine.kebir@insa-rouen.fr (N. Kebir).
http://dx.doi.org/10.1016/j.polymer.2015.04.046
0032-3861/© 2015 Elsevier Ltd. All rights reserved.

128
S. Bigot et al. / Polymer 66 (2015) 127e134
(ROP) of trimethylene carbonate (TMC) with zinc catalyst in pres-
ence of a diol [17,18]. Moreover, BHP can lead to a bifunctional
dibutyltindilaurate (95%), ethyl vinylether (99%), sodium ascorbate
(ꢀ98%) and copper sulphate pentahydrate (99.9%) were purchased
from Sigma Aldrich (France). 4-pentyn-1-ol (98%) and p-phenylene
diisothiocyanate (98%) were obtained from Alfa Aesar (France). 4-
hydroxybenzene ethanol (98%) was provided from Acros (France)
and benzoquinone (100%) from Merck (France).
chloro-telechelic polycarbonate (BCP) by esterification with
a-
chlorophenylacetyl chloride [16]. BHP and BCP are then used for
synthesis of triblock copolymers: PS-PC-PS and PMMA-PC-PMMA
by ATRP [16], or PLA-PC-PLA by reaction with lactide [15]. On the
other hand,
a,u-di-(cyclic carbonate) polycarbonate have been
prepared by Helou et al. [19] in three steps while Colonna et al. [20]
synthesized telechelic sulfonated polycarbonate ionomers by melt
polycondensation.
2.2. Instruments
NMR spectra were recorded on a Bruker Avance (300 MHz)
Spectrometer. IR spectra were recorded on a FTIR (PerkineElmer)
equipped with a diamond ATR device (attenuated total reflection).
Molecular weights and molecular weight distributions were
measured using size exclusion chromatography (SEC) on a Varian
PL-GPC50 device equipped with two mixed packed columns (PL gel
mixed type C). Dichloromethane was used as eluent at a flow rate of
1 mL minꢁ1 at 25 ꢂC and polystyrene standards were used for
calibration. Differential scanning calorimetry (DSC) was carried out
on a DSC Q2000 apparatus (TA Instruments). Samples were heated
from ꢁ90 ꢂC to 100 ꢂC under nitrogen using a heating rate of 10 ꢂC/
min. TGA measurements were performed on a TGA Q500 system
(TA Instruments) under nitrogen atmosphere. Samples were heated
from 30 ꢂC to 500 ꢂC using a rate of 10 ꢂC/min.
In this work, we describe a versatile two-step organocatalytic
synthesis of telechelic PCs bearing novel functionalities. In a first
step, methylcarbonate-ended PCs were synthesized from several
diols and an excess of DMC, in presence of BMIM-2-CO2 as catalyst.
Then, the methylcarbonate end-groups were reacted with hydroxyl
functionalized compounds bearing several chemical groups to
afford PCs with alkyne, alkene and phenol end-groups. The reac-
tivity of these groups towards polymerization was also studied
(Fig. 1).
2. Experimental section
2.1. Materials
Anhydrous dimethylcarbonate (ꢀ99%), 1,12-dodecanediol (99%),
2.3. Synthesis of BMIM-2-CO2
9-decen-1-ol
(97%),
(1,3-bis-(2,4,6-trimethylphenyl)-2-
imidazolidinylidene)
dichloro(o-isopropoxyphenylmethylene)
Catalyst was synthesized according to the procedure described
ruthenium (Hoveyda-Grubbs catalyst 2nd generation, 97%),
in literature [3]. 2.90 mL (22 mmol) of 1-n-butylimidazole, 4 mL
Fig. 1. Versatile approach for synthesis of new telechelic polycarbonates and their polymers.

S. Bigot et al. / Polymer 66 (2015) 127e134
129
(47.5 mmol) of dimethyl carbonate (DMC) and 25 mL of methanol
were introduced in a Schlenk tube under argon atmosphere. The
mixture was transferred via cannula to a 70 mL stainless steel batch
reactor previously purged under argon. The mixture was stirred
and heated to 135 ꢂC for 7 h. The mixture was then transferred into
a flask and methanol was evaporated under vacuum (trap-to-trap
distillation). The pale yellow viscous residue obtained was washed
with 4 ꢃ 20 mL of dry diethyl ether. The obtained solid was dried
overnight under vacuum to give pure BMIM-2-CO2 as a white
diethyl ether. After stirring for 1 h at room temperature, the reac-
tion mixture was washed with water and dried over MgSO4. The
solvent was then evaporated to afford 1,12-dimesyl-dodecane in
90e93% yields. Then, to a solution of 1,12-dimesyl-dodecane
(61 mmol of mesylate groups) in 140 mL of DMF, was added NaN3
(91.5 mmol). After stirring for 24 h at 75 ꢂC, the reaction mixture
was washed with 50 mL of water, extracted with diethyl ether
(6 ꢃ 50 mL) and dried over MgSO4. The solvent was then evapo-
rated to afford 1,12-diazido-dodecane in 88e90% yields. 1H NMR
powder in 66% yield. 1H NMR (D2O, 300 MHz,
d/ppm): 0.85 (m, 3H,
(300 MHz, CDCl3, d/ppm): 1.26e1.61 (m, 20H, CH2), 3.25 (t, 4H,
CH3eCH2), 1.23 (m, 2H, CH3eCH2), 1.75 (m, 2H, CH3eCH2eCH2),
3.89 (s, 3H, NeCH3), 4.33 (m, 2H, NeCH2), 7.32 (d, 1H, J ¼ 2.0 Hz,
CH]CHeNeCH2), 7.37 (d, 1H, J ¼ 2.0 Hz, CH]CHeNeCH3). 13C
CH2eN3). 13C NMR (75 MHz, CDCl3,
d/ppm): 25.1; 25.7; 27.8, 28.5,
30.7, 51.4. IR:
n
¼ 2091 cmꢁ1 (s, nN3).
NMR (D2O, 75 MHz,
140.3, 158.8.
d/ppm): 13.0, 19.2, 32.3, 36.8, 49.7, 122.1, 123.5,
2.6. Polymers synthesis
2.6.1. General procedure for synthesis of methyl carbonate
terminated PCs
2.3.1. Preparation of (9Z)-9-octadecene-1,12-diol (diol 1) [21]
To a solution of lithium aluminohydride (1.83 g, 48.1 mmol) in
75 mL of anhydrous diethyl ether, in a two-necked round bottom
flask with magnetic stirring under nitrogen atmosphere, methyl
ricinoleate (9.6 mmol) in 50 mL of anhydrous diethyl ether was
added. After stirring for 6 h at room temperature, hydrolysis of
lithioaluminate complexes was performed by dropwise addition of
water. The reaction mixture was washed with saturated aqueous
NaCl and dried over MgSO4. The solvent was then evaporated to
afford (9Z)-9-Octadecene-1,12-diol (yield: 81%). 1H NMR (300 MHz,
Under argon atmosphere, 1,12-dodecanediol (1.0 g, 5.02 mmol),
DMC (1.8 mL, 21.34 mmol) and
5 mol% of 1-n-butyl-3-
methylimidazolium-2-carboxylate (0.045 g, 0.2511 mmol) were
placed in a dried Schlenk tube equipped with a magnetic stirrer.
The reaction mixture was heated under stirring for 15 min at
100 ꢂC. The flask was then immersed in a heated oil bath at 150 ꢂC
for 6 h under vacuum, to carry out the polymerization. For linear
PCs (PC3-MC and PC4-MC), the reaction mixture was cooled and
the residue was purified by dissolving in THF and precipitating with
ethanol (yields: 85 and 80, respectively). The polymer was isolated
by filtration and dried under vacuum. Branched fatty PCs (PC1-MC
and PC2-MC) were viscous liquids and could not be precipitated.
CDCl3,
d
/ppm): 0.86 (t, 3H, J ¼ 7.15 Hz, CH3), 1.30 (m, 18H, CH2), 1.45
(m, 2H; CH2eCH2eCH(R)-OH), 1.55 (t, 2H,
J
¼
6.78 Hz;
CH2eCH2eOH), 2.04 (q, 2H, J ¼ 7.15 Hz; CH2eCH2eCH ¼ ), 2.20 (t,
2H, J ¼ 6.4 Hz; ¼CHeCH2eCH(R)-OH), 3.63 (m, 3H; CHeOH and
CH2eOH), 5.4 (m, 1H; CH]CH), 5.59 (m, 1H; CH]CH). 13C NMR
Characterizations of PC1-MC: 1H NMR (CDCl3, 300 MHz,
d/ppm):
0.86 (t, n ꢃ 3H, J ¼ 6.9 Hz, CH3eCH2), 1.28 (m, n ꢃ 18H, alkyl chain),
1.56e1.67 (m, n ꢃ 4H, CH2eCHeOeC]O, CH2eCH2eOeC]O), 2.01
(q, n ꢃ 2H, J ¼ 6.7 Hz, CH]CHeCH2eCH2), 2.32 (ded, n ꢃ 2H, J ¼ 6.
Hz, J ¼ 8.7 Hz, CHeCH2eCH]CH), 3.75 (s, 3H, CH2eOeC(¼O)e
OeCH3), 3.76 (s, 3H, CHeOeC(¼O)eOeCH3), 4.10 (t, n ꢃ 2H,
J ¼ 6.7 Hz, CH2eOeC]O), 4.68 (q, n ꢃ 1H, J ¼ 6.2 Hz, CHeOeC]O),
(75 MHz, CDCl3,
34.4, 35.9, 62.0, 70.6, 124.3, 132.5. IR (ATR):
disappearance of ester band at 1736 cmꢁ1
d/ppm): 13.2, 21.7, 24.8, 26.5, 28.3e28.7, 30.9, 31.8,
n
¼ 3327 cmꢁ1(s, nOH),
.
2.4. Preparation of fatty diol from methyloleate (diol 2)
5.43e5.52 (m, n ꢃ 2H, HC]CH). 13C NMR (CDCl3, 75 MHz,
d/ppm):
To a solution of methyloleate (17.7 mmol) in 100 mL of
dichloromethane, in an erlenmeyer with magnetic stirring at 0 ꢂC,
were added m-chloroperoxybenzoic acide (m-CPBA, 26.6 mmol).
After stirring for 3 h at 0 ꢂC, the reaction mixture was washed with
water and this aqueous phase was extracted with dichloromethane.
All organic phases were washed with warm water and dried
(MgSO4). The solvent was evaporated to afford epoxidized meth-
yloleate in 90e95 % yield. To a solution of lithium aluminohydride
(1.83 g, 48.1 mmol) in 75 mL of anhydrous diethyl ether, in a two-
necked round bottom flask with magnetic stirring under nitrogen
atmosphere, epoxidized methyl oleate (9.6 mmol) in 50 mL of
anhydrous diethyl ether was added. After stirring for 6 h at room
temperature, hydrolysis of lithioaluminate complexes was per-
formed by dropwise addition of water. The reaction mixture was
washed with saturated aqueous NaCl and dried (MgSO4). The sol-
vent was evaporated to afford the fatty diol in 80e85% yields. 1H
14.0, 22.5e33.7, 67.8, 67.9, 78.2, 123.7, 132.9, 155.1. IR (ATR):
n
¼ 1735 cmꢁ1 (s, ncarbonate),1445 cmꢁ1 (m, nmethyl carbonate end-goups).
Characterizations of PC2-MC: 1H NMR (CDCl3, 300 MHz,
d/ppm):
0.87 (t, n ꢃ 3H, J ¼ 6.5 Hz, CH3eCH2), 1.25 (m, n ꢃ 24H, alkyl chain),
1.55e1.65 (m, n ꢃ 6H, CH2eCHeOeC]O, CH2eCH2eOeC]O), 3.76
(s, 6H, CH2eOeC(¼O)eOeCH3, CHeOeC(¼O)eOeCH3), 4.10 (t,
n ꢃ 2H, J ¼ 6.5 Hz, CH2eOeC]O), 4.67 (q, n ꢃ 1H, J ¼ 5.6 Hz,
CHeOeC]O). 13C NMR (CDCl3, 75 MHz,
d
/ppm): 14.1, 22.7e34.0,
1735 cmꢁ1 (s, ncarbonate),
1445 cmꢁ1 (m, nmethyl carbonate end-goups).
Characterizations of PC3-MC: 1H NMR (CDCl3, 300 MHz,
68.0, 78.1, 155.3. IR (ATR):
n
¼
d/ppm):
1.26 (m, n ꢃ 12H, alkyl chain), 1.64 (q, n ꢃ 4H, J ¼ 7.2 Hz,
CH2eCH2eO), 3.75 (s, 6H, OeCH3), 4.11 (t, n ꢃ 4H, J ¼ 6.7 Hz,
CH2eO).13C NMR (CDCl3, 75 MHz,
d/ppm): 25.6, 28.6, 29.1, 29.4,
54.6, 68.0, 68.2, 155.4, 155.9. IR (ATR):
n
¼ 1735 cmꢁ1 (s, ncarbonate),
1445 cmꢁ1 (m, nmethyl carbonate end-goups).
NMR (300 MHz, CDCl3,
d
/ppm): 0.88 (s, 3H, J ¼ 6.72 Hz, CH3);
Characterizations of PC4-MC: 1H NMR (CDCl3, 300 MHz,
d/ppm):
1.24e1.59 (m, 30H, alkyl chain); 3.58 (m, 1H, CHeOH); 3.64 (m, 2H,
1.26 (m, n ꢃ 16H, alkyl chain), 1.65 (q, n ꢃ 4H, J ¼ 7.0 Hz,
CH2eOH). 13C NMR (75 MHz, CDCl3,
28.4e28.9, 31.0, 32.8, 37.1, 62.2, 71.2. IR (ATR):
nOH), disappearance of ester band at 1740 cmꢁ1
d/ppm): 13.2, 21.8, 25.3, 26.0,
CH2eCH2eO), 3.77 (s, 6H, OeCH3), 4.11 (t, n ꢃ 4H, J ¼ 6.7 Hz,
n
¼ 3338 cmꢁ1(s,
CH2eO).13C NMR (CDCl3, 75 MHz,
d/ppm): 24.8, 27.8, 28.3, 28.6,
.
53.7, 67.1, 67.3154.6, 155.0. IR (ATR):
n
¼ 1735 cmꢁ1 (s, ncarbonate),
1445 cmꢁ1 (m, nmethyl carbonate end-goups).
2.5. Preparation of 1,12-diazidododecane
2.6.2. General procedure for chain-ends functionalization
In a two-necked round bottom flask equipped with a magnetic
stirring and a nitrogen flow, 6.0 mL of Et3N (45.5 mmol) followed by
3.9 mL (50.0 mmol) of mesyl chloride were added in a dropwise
manner to a solution of dodecane-1,12-diol (22.7 mmol) in 50 mL of
Under argon atmosphere, methylcarbonate terminated PC
(0.5 g, 0.278 mmol), 9-decenen-1-ol or 4-hexyn-1-ol or 4-
hydroxybenzene ethanol (3 eq, 0.833 mmol) and 5 mol% of 1-n-
butyl-3-methylimidazolium-2-carboxylate (4.0 mg, 0.0139 mmol)

130
S. Bigot et al. / Polymer 66 (2015) 127e134
were placed in a dried Schlenk tube equipped with a magnetic
stirrer. The reaction mixture was heated under stirring for 15 min at
100 ꢂC. The flask was then immersed in a heated oil bath at 150 ꢂC
for 6 h under vacuum. Then, the reaction mixture was cooled and
the residue was purified by dissolving in THF and precipitating with
ethanol. The polymer was isolated by filtration and dried under
vacuum.
nC¼C) and between 800 and 900 cmꢁ1 (w, gCeH), disappearance of
isothiocyanate band at 2090 cmꢁ1
.
2.8. Reactivity study of alkyne end-groups towards click
cycloaddition with diazide
In a round bottom flask, alkyne terminated polycarbonate (PC4-
alkyne) (0.4 g, 2.10ꢁ5 mol) and 1,12-diazidododecane (1.1 eq) were
dissolved in 24 mL of THF at 50 ꢂC. After, 0.05 eq of CuSO4 and 0.02
eq of sodium ascorbate were added. Then, the polymerization re-
action was conducted at 50 ꢂC for 24 h, under magnetic stirring. The
polymer started to precipitate in the medium after only 4 h of re-
action. Finally, HDC Polymer was recovered by filtration and dried
Characterizations of PC4-alkene: (yield: 84%) 1H NMR (CDCl3,
300 MHz,
d
/ppm): 1.26 (m, n ꢃ 16Hþ8H, alkyl chain), 1.65 (q,
n ꢃ 4H, J ¼ 6.9 Hz, CH2eCH2eO), 2.03 (q, 4H, J ¼ 6.18 Hz, CH2eCH]
CH2), 3.71 (t, 4H, J ¼ 6.7 Hz, OeCH2 end-groups), 4.11 (t, n ꢃ 4H,
J ¼ 6.6 Hz, OeCH2), 4.95 (ded, 4H, J ¼ 20.3 and J ¼ 11.4 Hz, CH]
CH2), 5.80 (m, 2H, CH]CH2). 13C NMR (CDCl3, 75 MHz,
d/ppm):
24.8, 27.8, 27.9, 28.1, 28.3, 28.6, 28.6, 31.9, 32.9, 52.5, 67.1, 113.2,
138.2, 154.5. IR (ATR): Disappearance of the band of the methyl
under vacuum (yield: 90%). IR (ATR):
n
¼ 1736 cmꢁ1 (s, ncarbonate),
disappearance of azide band at 2100 cmꢁ1
.
carbonate end-groups at 1445 cmꢁ1
.
Characterizations of PC4-phenol: (yield: 88%) 1H NMR (CDCl3,
300 MHz,
3. Results and discussions
d
/ppm): 1.26 (m, n ꢃ 16H, alkyl chain), 1.66 (q, n ꢃ 4H,
J ¼ 7.1 Hz, CH2eCH2eO), 2.90 (t, 4H, J ¼ 7.2 Hz, CH2-Ph), 4.11 (t,
n ꢃ 4H, J ¼ 6.7 Hz, OeCH2), 4.28 (t, 4H, J ¼ 7.2 Hz, OeCH2eCH2-
Ph), 6.78 (m, 4H, aromatics CH]C(OH)eCH), 7.1 (m, 4H, aro-
3.1. Synthesis and properties of methylcarbonate telechelic
polycarbonate
matics CHeCH]C(OH)eCH]CH). 13C NMR (CDCl3, 75 MHz,
d
/
Methylcarbonate terminated polycarbonates were prepared by
polycondensation reaction of an excess of DMC with a diol in
presence of BMIM-2-CO2 as a metal-free catalyst. The use of this
kind of catalyst in polymerization processes especially for medical
application (where metal atoms can be forbidden in the future) is of
great interest [24]. Several branched (1 and 2) and linear (3 and 4)
diols were tested. 1,10-decanediol (3) and 1,12-dodecanediol (4) are
commercially available diols. (9Z)-9-Octadecene-1,12-diol (1) was
obtained by reduction of methyl ricinoleate with LiAlH4. The second
fatty diol (2) was obtained by epoxidation of the double bond of
methyl oleate followed by reduction of both epoxide and ester
groups with LiAlH4. The product is statistically a mixture of octa-
decane-1,9-diol and octadecane-1,10-diol.
ppm): 24.8, 27.8, 28.3, 28.5, 28.6, 33.4, 67.1, 114.5, 129.2, 154.6. IR
(ATR): aromatic bands between 1500 and 1600 cmꢁ1, disap-
pearance of the band of the methyl carbonate end-groups at
1445 cmꢁ1
.
Characterizations of PC4-alkyne: (yield: 95%) 1H NMR (CDCl3,
300 MHz,
d
/ppm): 1.26 (m, n ꢃ 16Hþ8H, alkyl chain), 1.65 (q,
n ꢃ 4H, J ¼ 6.9 Hz, CH2eCH2eO), 3.65 (t, 4H, J ¼ 6.7 Hz, OeCH2
chain-ends), 4.11 (t, n ꢃ 4H, J ¼ 6.6 Hz, OeCH2). 13C NMR (CDCl3,
75 MHz, d/ppm): 24.8, 27.8, 28.3, 28.6, 28.6, 67.1, 154.5. IR (ATR):
Disappearance of the band of the methyl carbonate end-groups at
1445 cmꢁ1
.
2.6.3. Reactivity study of alkene ends groups by ADMET
polymerization
As described by Naik et al. [3], the polymerization reaction oc-
curs according to a two-stage procedure. Firstly, the reaction me-
dium was heated to 100 ꢂC during t1 minutes to allow the in-situ
formation of the NHC active species by decarboxylation of BMIM-2-
CO2. Then, the polycondensation reaction (based on a trans-
esterification process) was performed at 150 ꢂC during t2 hours
under vaccum. These conditions favour the continuous elimination
of the formed methanol. However, because of the volatility of DMC
in these operating conditions, the use of a large excess of DMC was
necessary to get methylcarbonate end-groups. Thus, a similar
mechanism to that suggested in the past by Naik et al. [3], is also
expected.
In order to use same polymerization conditions for all the cho-
sen diols, and because the presence of secondary alcohol in the
branched diols suggesting a lower reactivity, the reaction param-
eters were optimized using the branched diol 1 (Supporting Data).
It was found that the optimal conditions leading to a total con-
version of alcohol groups into methyl carbonate groups and to
homogeneous SEC chromatogram with dispersity Ð close to 2 are
the following:
Metathesis was carried out as described by Firdaus and Meier
[23]. Alkene terminated polycarbonate (PC4-alkene) (0.4 g,
1.36$10ꢁ4 mol) and 1,4-benzoquinone (2 mol%) were introduced in
a round bottom flask equipped with a magnetic stirrer. The mixture
was stirred 5 min at 80 ꢂC. Then, (1,3-bis-(2,4,6-trimethylphenyl)-
2-imidazolidinylidene) dichloro(o-isopropoxyphenylmethylene)
ruthenium (Hoveyda-Grubbs catalyst 2nd generation) was added.
The reaction was carried out at 80 ꢂC under vacuum. After 4 h, the
mixture was dissolved in THF and an excess of ethyl vinyl ether was
used to quench the reaction. ADMET Polymer was purified by
precipitation in ethanol and filtration (yield: 87%). 1H NMR (CDCl3,
300 MHz,
d
/ppm): 1.26 (m, 16Hþ8H, alkyl chain), 1.64 (q, 4H,
J ¼ 6.9 Hz, CH2eCH2eO), 1.96 (m, mx4H, CH2eCH]CH), 3.63 (t, 4H,
J ¼ OeCH2), 4.11 (t, 4H, J ¼ 6.7 Hz, OeCH2), 5.37 (m, 2H, CH]CH). 13
C
NMR (CDCl3, 75 MHz, d/ppm): 24.8, 27.8, 28.3, 28.6, 28.6, 31.9, 67.1,
154.5. IR (ATR):
n
¼ 1735 cmꢁ1 (s, ncarbonate).
2.7. Reactivity study of phenol end-groups towards
diisothiocyanates
- molar percentage of BMIM-2-CO2: 5%;
- excess of DMC: 4.5 eq;
Phenol terminated polycarbonate (PC4-phenol) was dissolved in
THF (1 g mLꢁ1). The catalyst (DBTL) was added to the solutions in a
ratio of [DBTL]/[OH] ¼ 0.05. Then, p-phenylene diisothiocyanate
was added in last with an effective ratio of [NCS]/[OH] ¼ 1.05. The
different solutions were cast in PTFE moulds under dried argon
atmosphere for 2 h. The films formed (Poly(thio-urethane)) after
solvent evaporation were cured for 22 h at 60 ꢂC (yield: 100%). IR
- time of catalyst activation at 100 ꢂC (t1): 15 min;
- reaction time at 150 ꢂC (t2): 6 h.
FTIR analysis of the obtained PCs showed mainly the presence of
the carbonyl band of carbonate function at around 1736 cmꢁ1 and a
characteristic band of methyl carbonate end groups at 1445 cmꢁ1
.
(ATR):
n
¼ 3447 cmꢁ1 (w, nNH),
n
¼ 1736 cmꢁ1 (s, ncarbonate and
The FTIR spectrum of PC4-MC is shown in Fig. 2 as a typical
example.
nthiocarbamate), aromatic bands between 1500 and 1600 cmꢁ1 (w,

S. Bigot et al. / Polymer 66 (2015) 127e134
131
Mn ¼ Mchainꢁends þ Mrepeating unit ꢃ Pn
(2)
where:
- Mchain-ends is the molecular weight of the chain-ends.
- Mrepeating unit is the molecular weight of the polymer repeating
unit.
- ICH2O is the relative integrations of the peaks arising from pro-
tons in a position to the oxygen of the carbonate linkage (around
4.10 ppm); y: is the number of theses protons.
- Ichain-ends is the relative integration of protons of the end-groups;
x: is the number of these protons.
Using the Carothers equation (with p ¼ 1), we can also calculate
the effective stoechiometric coefficient of DMC (1/r) used during
the polymerization process, as follows (Table 1):
1
r
Pn þ 1
Pn ꢁ 1
¼
(3)
Fig. 2. Selected zones of the FTIR spectra of the prepared telechelic PCs.
Molecular weights (Mn and Mw) and dispersity (Ð) were also
determined by SEC, using polystyrene (PS) standard calibration,
and are depicted in Table 1.
The NMR analysis showed a total conversion of the alcohol
groups into carbonate groups. The 1H NMR spectrum of PC4-MC is
depicted in Fig. 3. Therefore, we can assume that all PC chains
contain two carbonate end-groups (conversion: p ¼ 1). Thus, the
absolute values of the polymerization degree (Pn) and average
molecular weight (Mn) of the prepared polycarbonates were
calculated from 1H NMR spectra (Table 1) as follows:
One can observe that 1/r values were comprised between 1.10
and 1.31, which is far from the started DMC stoechiometric coeffi-
cient of 4.50 (Table 1). Absolute Mn values were comprised be-
tween 1100 and 6900 g/mol. The methylcarbonate terminated PCs
based on saturated and unsaturated fatty diols (PC1-MC and PC2-
MC) exhibited lower 1/r values and higher Pn and Mn values
comparing to the PCs based on 1,10-decanediol (PC3-MC) and 1,12-
dodecanediol (PC4-MC). Furthermore, the branched biobased PCs
being viscous liquids, they could not be precipitated, which ex-
plains their larger dispersity (Ð ꢀ 2.0) in comparison with the
precipitated linear PCs (Ð ~ 1.3).
ICH O ꢃ x
2
Pn ¼
(1)
y ꢃ Ichainꢁends
Fig. 3. 1H NMR spectra of PC4-MC, PC4-alkene and ADMET polymer.

132
S. Bigot et al. / Polymer 66 (2015) 127e134
Table 1
Physico-chemical properties of the prepared telechelic PCs.
Diol
End-groups
1H NMR
SEC
TGA
DSCc
Pn
1/rd
Mn
6900
Mn
Ð
T5% (ꢂC)
Tmax (ꢂC)
Tg (ꢂC)
Tm (ꢂC)
D
Hm (J/g)
Tc (ꢂC)
D
Hc (J/g)
PC1-MC
PC2-MC
PC3-MC
PC4-MC
1
2
3
4
4
4
4
4
Methyl arbonate
Methyl carbonate
Methyl carbonate
Methyl carbonate
Methyl carbonate
Alkene
22
18
5
7
10
9
1.10
1.12
1.50
1.31
1.21
1.25
1.11
1.04
5300
3800
2500
3300
4500
4500
8900
23,100
2.0
2.9
1.6
1.3
1.7
1.3
1.7
2.0
278
278
/
266
/
284
326
328
317
322
/
373
/
374
373
374
ꢁ68
/
/
24
/
/
22
5700
1100
1800
2500
2400
4500
12000b
ꢁ52
ꢁ9
30 (45)
60
/
60
ꢁ18
16 (30)
51
/
51
/
/
/
/
/
/
108
119
/
123
88
104
114
/
114
88
PC4-MC controla
PC4-alkene
PC4-phenol
PC4-alkyne
Phenol
Alkyne
18
65
68
53
54
52b
83
88
a
Conditions of the second step applied in absence of functional molecules.
Calculated using Benoit factor and not from the NMR spectrum because of very weak signals of the chain-end protons.
Data from second cycle.
b
c
d
1/r is the calculated effective stoechiometric coefficient of DMC monomer towards diol monomer.
Thermal gravimetric analysis (TGA) of methylcarbonate termi-
nated PCs revealed that all these polymers possess a good thermal
stability up to 200 ꢂC, with T5% ranging from 266 to 278 ꢂC and
T
max ranging from 317 to 373 ꢂC (Table 1). The TGA thermogram of
PC4-MC is shown in Fig. 4 as example. DSC results revealed that
polycarbonate based on unsaturated branched fatty diol (PC1-MC)
was totally amorphous with Tg ¼ ꢁ68 ꢂC. On the other hand, PC2-
MC, based on saturated branched fatty diol, exhibited a semi-
crystalline behaviour with Tg of ꢁ52ꢂ and Tm of ꢁ9 ꢂC. These
negative values can be explained by a plasticizing effect of the side
chains, which increase the free volume. Furthermore, the presence
of both of carbonecarbon double bond and hexyl side chain in
PC1-MC disturbed polymer chain organization leading to absence
of crystalline domains. This phenomenon has already been
observed in the case of polyurethane [22] and polyamide [21]
materials based on (9Z)-9-Octadecene-1,12-diol (diol 1) or its
corresponding diamine. On the other hand, the linear PC3-MC and
PC4-MC were also semi-crystalline with Tm values of 30 (second
peak at 45 ꢂC) and 60 ꢂC, respectively; however, their Tg were not
observed.
3.2. Synthesis and properties of alkyne, alkene and phenol telechelic
polycarbonate
The introduction of new functionalities through chain-end
chemical modifications was achieved on PC4-MC (based on 1,12-
dodecanediol), used as representative polymer. This methylcar-
bonate terminated PC was reacted with an optimized excess (3 eq)
of 9-decen-1-ol, 4-hexyn-1-ol or 4-hydroxybenzene ethanol, in
presence of BMIM-2-CO2 as catalyst (5%mol). The new telechelic
polycarbonates were obtained after heating at 100 ꢂC during 15 min
and then at 150 ꢂC for 6 h under vacuum.
It is noteworthy that the addition of these functional molecules
as chain limiter to the starting mixture of diol and DMC (one shot
process), in an amount to get a molecular weight around 2000 g/
mol, led to polycarbonates with heterogeneous chain-ends. Indeed,
residual methylcarbonate chain-ends were observed in this case.
On the other hand, the process of two reactions of 6 h led to product
without detectable amounts of methyl groups.
The total conversion of methyl carbonate was first evidenced by
NMR spectroscopy. Indeed, the peaks corresponding to the methyl
carbonate groups at 3.77 ppm in 1H NMR spectrum (Fig. 3) and at
155 ppm in 13C NMR spectrum, have totally disappeared. Unlike
alkyne chain-ends, the phenol and alkene chain-ends exhibited
well distinguished NMR signals allowing Mn calculations. More-
over, FTIR showed also the disappearance of the band at 1445 cmꢁ1
corresponding to distortion of CeH bonds of the methylcarbonate
groups (Fig. 2). The presence of phenol end-groups was also easily
Fig. 4. TGA traces of the prepared telechelic PCs and their polymers.

S. Bigot et al. / Polymer 66 (2015) 127e134
133
Fig. 5. FTIR spectra of ADMET polymer, poly(thio-urethane) and HDC polymer.
evidenced by the band at 1515 cmꢁ1 arising from aromatic double
bonds.
PC4-alkene was self-polymerized through ADMET reaction,
using ruthenium Hoveyda-Grubbs catalyst (2nd generation). The
reaction was performed under neat conditions for 4 h at 80 ꢂC
under vacuum. Then, the mixture was dissolved in THF and an
excess of ethyl vinyl ether was added to quench the reaction.
The 1H NMR spectrum of the obtained ADMET Polymer (Fig. 3)
revealed the disappearance of vinyl group signals at 4.95 and
5.80 ppm and the appearance of a signal at 5.37 ppm arising
from ethylenic protons. However, the FTIR spectrums of ADMET
Polymer and PC4-alkene were very close (Figs. 2 and 5). The SEC
chromatogram of ADMET Polymer compared to those of PC4-
alkene and PC4-MC is shown in Fig. 6. The Mn value of
ADMET Polymer was of 11,200 g/mol while the Mn value of its
precursor PC4-alkene was of 2400 g/mol (Tables 1 and 2). TGA
and DSC analysis (Fig. 4, Tables 1 and 2) showed that ADMET
Polymer and PC4-alkene have very close thermal properties
(Fig. 6).
The phenol terminated polycarbonate (PC4-phenol) was reac-
ted with p-phenylene diisothiocyanate, in the presence of DBTL as
catalyst, to afford Poly(thio-urethane). THF solutions of the
starting mixture were casted in a PTFE mould for 2 h at room
temperature under argon atmosphere. The material obtained after
solvent evaporation was next cured for 22 h at 60 ꢂC. However,
the obtained polymer was not well soluble in common organic
Molecular weights of the functionalized polycarbonates were
assessed by SEC and by 1H NMR using Equation (1). Results are
depicted in Table 1. One can observe that Mn increased after chain-
end derivatization. The Mn seemed to be affected by the nature of
the functional molecule used for derivatization. The more volatile
was this molecule, the higher was the Mn of the obtained telechelic
polycarbonate. Indeed, 9-decen-1-ol (mp
¼
13 ꢂC and
bp ¼ 234e238 ꢂC at atmospheric pressure) and 4-hydroxybenzene
ethanol (mp ¼ 89e92 ꢂC and bp ¼ 190 ꢂC under 18 mm Hg) did not
remove easily at 150 ꢂC under vacuum, unlike 4-hexyn-1-ol, which
has a boiling point of 150 ꢂC at atmospheric pressure. Actually, PC4-
alkene, PC4-phenol and PC4-alkyne exhibited SEC Mn values of
4500, 8900 and 23,100 g/mol, respectively. This result suggests that
chain extension occurred independently on the presence of these
molecules. To attest this hypothesis, the conditions of chain-end
derivatization were applied on PC4-MC alone, in the presence of
catalyst (Table 1, PC4-MC control). As expected, an increase of Mn
was observed. This result suggested a displacement of a trans-
esterification equilibrated system towards elimination of DMC
leading to chain extension.
It is noteworthy that the Mn values of linear polycarbonates
obtained by SEC evolve linearly with the Mn values obtained by 1H
NMR. The equation slope which is called the Benoit Factor [25,26] is
of 1.93. In this respect, the absolute Mn value of PC4-alkyne, which
could not be directly determined by 1H NMR because of very weak
chain-ends signals, could be calculated through the Benoit Factor,
i.e. Mn ¼ 11,970 g/mol (Pn ¼ 52).
TGA analysis revealed that the new telechelic PCs were more
thermally stable than their methylcarbonate terminated precursor
(PC4-MC), with regards to temperature values at 5% of degradation
(Table 1). The TGA traces of these oligomers are presented in Fig. 4.
Furthermore, DSC analysis showed that chain-ends functionaliza-
tion with phenol and alkyne groups led to slight increase of
melting points of the crystalline zones, associated with a slight
decrease of the melting enthalpy, suggesting a slight decrease of
crystallinity.
3.3. Synthesis and properties of polymers from the prepared
telechelic polycarbonates
The reactivity of the polycarbonate end-groups was tested
towards polymerization.
Fig. 6. SEC chromatograms of PC4-MC, PC4-alkene and ADMET polymer.

134
S. Bigot et al. / Polymer 66 (2015) 127e134
Table 2
Physico-chemical properties of ADMET polymer, poly(thio-urethane) and HDC polymer.
Polymer code
Precursor
SEC
TGA
DSCc
Mn
Ð
T5% (ꢂC)
Tmax (ꢂC)
Tg (ꢂC)
Tm (ꢂC)
DHm (J/g)
Tc (ꢂC)
DHc (J/g)
b
ADMET polymer
Poly(thio-urethane)
HDC polymer
PC4-alkene
PC4-phenol
PC4-alkyne
11,200
1.8
305
270
319
372
349
369
/
/
/
61
62
67
106
87
76
49
48
53
89
90
77
a
a
b
/
/
a
a
b
/
/
a
Polymer was not well soluble in SEC solvents.
Tg was not observed.
Data from second cycle.
b
c
solvents for SEC and NMR analysis. On the other hand, the FTIR
analysis showed the total disappearance of the isothiocyanate
band at 2090 cmꢁ1, and the appearance of supplemental aromatic
bands at 1550 and 852 cmꢁ1 ascribed to the reacted p-phenylene
diisothiocyanate. The valence vibration band of NeH bond of the
thio-urethane function was observed at 3447 cmꢁ1, whereas the
carbonyl band of thio-urethane function was overlapped with the
carbonyl band of carbonate function at 1736 cmꢁ1. TGA analysis
showed that Poly(thio-urethane) was less thermally stable than
its precursor PC4-phenol (Fig. 4). Actually, T5% of Poly(thio-
urethane) was of 270 ꢂC against 326 ꢂC for PC4-phenol
(Tables 1 and 2). This is due to the fragility of the thio-urethane
function comparing to the carbonate one. Furthermore, because
p-phenylene diisothiocyanate is present in Poly(thio-urethane) at
only 4 wt%, the melting and crytallization temperatures of this
polymer are those of the polycarbonate segment, i.e. close to
those of PC4-phenol.
Finally, the reactivity of alkyne end-groups of PC4-alkyne was
studied towards the CuI-catalysed Huisgen 1,3-dipolar cycloaddi-
tion (HDC) with 1,12-diazidododecane. 1,12-diazidododecane was
prepared through a classical pathway consisting in the reaction of
mesyl chloride with 1,12-dodecanediol, and then the displacement
of the mesylate groups with sodium azide in organic medium. The
polymerization reaction by HDC was conducted at 50 ꢂC for 24 h in
THF medium, in presence of the mixture CuSO4/sodium ascorbate
as catalyst. It is noteworthy that the HDC Polymer started to
precipitate in the medium after only 4 h of reaction. HDC Polymer
was also not well soluble in common organic solvents for NMR
and SEC analysis. The FTIR spectrum of HDC Polymer showed
mainly the disappearance of the band of the azide group at
2100 cmꢁ1. Moreover, because of HDC Polymer is based on only
2 wt% of 1,12-diazidododecane, their thermal properties (Fig. 4,
Tables 1 and 2) were very close to those of the polycarbonate
chains (PC4-alkyne).
Acknowledgements
This work was a part of the project “VegePolTech” in the frame-
ꢀ
ꢀ
work of the European program “Fonds Europeen de Developpement
ꢀ
Economique Regional (FEDER)”. Authors thank Europe and the
“Haute Normandie” region for their financial support.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.polymer.2015.04.046.
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